DE102007033460A1 - Circular process for the production of barium sulfate and lithium metal phosphate compounds - Google Patents

Abstract

The present invention relates to a cyclic process for the preparation of barium sulfate and lithium iron phosphate, comprising (i) providing an aqueous, lithium and sulfation-containing solution and (ii) adding solid barium hydroxide at a temperature of greater than 50 ° C and (iii) the Barium hydroxide is added over a period of less than 15 minutes. Furthermore, the present invention relates to barium sulfate obtainable by the process according to the invention.

Description

The The present invention relates to a process for the preparation of Barium sulfate and lithium metal phosphates.

Both barium sulfate and lithium metal phosphates have great industrial significance:
Barium sulfate is used in particular for the production of photographic papers, paints and plastics and in medical diagnostics and in medical plastics. Barium sulphate is a high-quality, pure white inert, acid and alkali-resistant filler that is extremely weather-resistant.

barium sulfate with a high so-called "whiteness", with smaller specific surface and low oil absorption number and good dispersibility is referred to as "blanc fixe" and serves as white pigment and filler.

Particularly high quality and finely divided "Blanc Fixe" types are also used in cosmetics and sunscreen creams ( WO 01/92157 ). Further details on "Blanc Fixe" are for example from J. Hocken in Euro Coat, Lyon 9/97 pages 1 to 14 discussed.

by virtue of its high absorption for X-rays and Its high biological inertia also serves as a medical Contrast agent.

Blanc Fixe types with an average particle size of 0.5 to 1 μm and narrow grain band, ie in particular with a monomodal particle size distribution have maximum light scattering effect and are therefore particularly well suited as white pigment or replacement material for titanium white. ( Machunsky, E. Winkler, J., Polymers Paint Color Journal (1990) 180, 350-354 ).

Blanc Fixe is usually made on an industrial scale Reaction of sodium hydroxide solution and sulfuric acid or sodium sulfate solutions with aqueous solutions of barium chloride or Barium sulfide prepared. The particle morphology is adjusted by adjusting the reaction conditions such as temperature, concentration, pH, Mixing and stirring speeds, addition of seed crystals or also adjusted by organic additives.

In particular, organic additives have recently been used to improve the particle morphology of barium sulfate ( WO 01/58809 ).

In terms of the purity of the starting solutions in the production of "Blanc Fixed ", in particular concerning the presence of the Whiteness affecting metals (eg transition metals and heavy metals), there are high demands on products to get a high degree of whiteness.

According to the WO 00/76919 Barium sulfate can also be prepared from dissolved barium hydroxide with sulfuric acid, which is economically not very attractive in addition to high raw material costs due to the poor solubility of barium hydroxide.

Lithium metal phosphate compounds, in particular lithium transition metal phosphate compounds, have recently become widely used as cathode and anode materials in batteries ( US 5,910,382 . WO 02/099913 ).

Besides solid-state syntheses, wet-chemical methods for the preparation of such compounds are also used, as exemplified in US Pat DE-10353266 or in the WO 02/083555 are described. In such wet-chemical processes, the particle morphology of the lithium transition metal phosphate produced can be controlled particularly advantageously. Lithium hydroxide is often used as raw material in these processes, which is brought together in one of the synthesis steps with an acidic solution containing phosphoric acid and at least one transition metal sulfate. However, a problem in the production of lithium transition metal phosphates by such wet-chemical processes was in particular the high loss of lithium ions in the so-called spent liquor, whose renewed use in typical industrial cycle processes, especially in the workup and recovery of the starting materials by high levels of foreign ions, especially sulfate, difficult ,

So far were only extremely expensive cleaning procedures known to a reprocessing of the lithium-containing waste liquor to enable.

It Therefore, it was an object of the present invention, a To create a process that ensures economic and efficient reuse and treatment of lithium- and sulphate-containing wastewater allows.

• (i) Bereitstellens einer wässrigen lithium- und sulfationenhaltigen Lösung und
• (ii) Zugabe festen Bariumhydroxids bei einer Temperatur von mehr als 50°C
• (iii) wobei die Zugabe des Bariumhydroxids über einen Zeitraum von weniger als 15 Minuten erfolgt.

This object is achieved by a process which provides a cyclic process for the preparation of barium sulfate and lithium transition metal phosphates, comprising the steps of

• (i) providing an aqueous solution containing lithium and sulfation, and
• (ii) adding solid barium hydroxide at a temperature greater than 50 ° C
• (iii) wherein the addition of the barium hydroxide occurs over a period of less than 15 minutes.

Surprisingly, it was found that an almost complete recovery of the valuable lithium component compared to previously known precipitation techniques is possible, which allow only incomplete recovery, since there are no absolutely sparingly soluble lithium compounds. In addition, surprisingly, a phase-pure barium sulfate of high whiteness and uniformly fine-grained particle morphology, which meets the high requirements of a "Blanc Fixe" quality.

Especially the barium sulphate thus obtained has the name for "Blanc Fixed "required particle size distribution and a low specific surface area without the need for crystallization aids like seed crystals or the addition of organic additives must become. This result of the invention Procedure was not expected in this form. Because as known to the expert is, leads the very low solubility product of barium sulfate during the precipitation reaction normally to very high supersaturations and nucleation rates, which in turn is extremely high surface area and highly agglomerated Precipitates with high specific surface area entail.

The Precipitated barium sulfate can be used economically as a white pigment be used. The solid precipitate is from the Mother liquor for example by filtration or centrifugation or other methods which appear to be suitable for a person skilled in the art and optionally washed, wherein a concentrated lithium hydroxide solution obtained as mother liquor, the subsequent ßend at the subsequent wet-chemical synthesis of lithium transition metal phosphates can be reused.

The Addition of solid barium hydroxide has the advantage that the obtained Lithium hydroxide solution is not unnecessarily diluted will, so that usually no additional energy-consuming Concentration of the lithium hydroxide solution before her Reuse is necessary.

Especially is advantageous in the method according to the invention, that no further alkali ions in the mother liquor or in the precipitate containing both the lithium salt solution or the Barium sulfate would contaminate.

The diluted washing solution in the inventive Process optionally when washing the separated barium sulfate is obtained is free of interfering foreign ions and z. After an additional concentration step as well be added back to the mother liquor.

The inventive method allows thereby a practically complete lithium or lithium ion recovery, as is the case with other methods known from the prior art is possible.

The Barium sulfate obtained in the process according to the invention is particularly phase-pure and almost free of interfering iron ions, which cause a yellowing and can directly as "Blanc Fixed "quality to be used.

The Addition of the solid barium hydroxide is carried out according to the invention a temperature of more than 50 ° C, more preferably above 75-80 ° C. Below 50 ° C typically will not be particle morphologies and distributions of the barium sulfate, which has a use as "blanc Fixe ".

Further It is important that the addition of barium hydroxide in less than 15 minutes, preferably completed in less than 5 minutes, so that the precipitation takes place quickly, which also the desired particle morphology positively influenced.

While the addition of the barium hydroxide and at least until completion the precipitation reaction, the mixture is stirred, to a sedimentation of the barium hydroxide or the precipitate used to prevent.

The barium sulfate obtainable by the process according to the invention has a very high whiteness of greater than 95, preferably greater than 97 and more preferably greater than 99, and a low specific surface area of less than 15 m ² / g, very particularly preferably less than 10 m ² / g ,

Preferably the barium sulfate obtained is alkali-free and also chloride-free and sulfide-free, so that the purity of the means of the invention Barium sulfate obtained is particularly high.

In very particularly preferred embodiments of the invention, the barium sulfate obtained has a particle size in the range of 0.5 to 1 .mu.m, wherein the particle distribution is particularly preferably monomodal and the D ₅₀ value preferably between 0.4-0.8 microns, most preferably at 0.6 microns.

Surprisingly was found that with the inventive Process a low iron barium sulfate with high whiteness even if that was used as the starting solution Lithium sulfate wastewater from a production process of an iron-containing Lithium metal phosphate originates.

After the precipitation and separation of the barium sulfate, the solution containing lithium hydroxide is again fed to a wet-chemical production process of lithium iron phosphate, as he z. B. in the DE 10353266 or in the WO 02/083555 is described. Of course, any other lithium transition metal phosphate can be prepared as well. Preferred transition metals in addition to iron, which are preferably used in the form of their sulfates are Mn, Co, Ni, and V and any combinations thereof. Particularly preferred combinations are those of Fe and Mn, or Co.

The The inventive method optionally also includes a pretreatment of the lithium sulfate-containing wastewater the precipitation of barium sulfate. For this purpose, the wastewater by adding lithium hydroxide to a pH between 8 and 2, preferably between 7 and 4 brought to the phosphate content To reduce precipitation of lithium phosphate and eventual Precipitate foreign metal ions as hydroxides. The precipitate For example, by filtration, centrifugation or others those skilled in the seem appropriate methods of the lithium sulfate separated mother liquor separated. The basic adjusted mother liquor can also be fed to a concentration by reverse osmosis. For this purpose, it is preferably by addition of sulfuric acid neutralized again (pH 7-8) or slightly acidified (pH 4-6). Because this very economical process for the concentration of solutions namely advantageously carried out with neutral or slightly acidic solutions and therefore also advantageous in the lithiumsulfathaltigen mother liquor before the barium sulfate precipitation and not at the basic Lithium hydroxide solution after barium sulfate precipitation carried out.

The separated precipitate is disposed of appropriately or in the case of lithium phosphate again as a raw material for the production used by, for example, lithium transition metal phosphates. Preferably If this is done by acidification, preferably with phosphoric acid, converted to easily soluble lithium hydrogen phosphate.

As the expert is known, the residual content of sulfate ions or to barium ions obtained in the barium sulfate precipitation Lithium hydroxide solution through the stoichiometric Ratio of the barium hydroxide used in the Solution containing lithium sulfate and by the completeness the precipitation reaction determined. This requires an accurate Control of the contents and amounts of reactants. As barium hydroxide in Form of different hydrates with changing water content and depending on the state of aging with varying carbonate content occur can, provides the inventive method also a simple rule that can be performed by the operator himself for direct control of the precipitation result.

there is the reaction vessel after completion of the precipitation reaction taken a sample of the suspension and in a laboratory slide on Filtration of a microfiltration membrane. The filtrate is with Hydrochloric acid and neutralized on two test tubes A and B distributed. To test tube A, a few drops of a saturated Barium chloride solution added while to test tube B a few drops of a saturated solution of lithium sulfate be added. If test tube A shows a strong haze, so is a high residual content of sulfate before and it must by adding corrected further barium hydroxide to the reaction vessel become. If test tube B shows a strong haze, it is obvious high residual content of barium before and it must by adding another Be corrected lithium sulfate solution. The procedure can iteratively until both test tubes are empty or show only slight turbidity, and a lithium hydroxide solution of good purity. As a rule, one becomes a low one Barium content give preference and rather a slight haze in test tube A accept.

With The test procedure can also check the completeness of the precipitation reaction become. For this, the filter cake is removed from the filter and remelted in demineralized water and for further stirred for at least 10 minutes. This suspension will filtered again in the previously cleaned filter and the filtrate as examined above. If test tube B shows a haze, so the suspension contains unreacted solid Barium hydroxide and the mixture in the reaction vessel must to be stirred further.

Subsequently, the thus obtained in a few simple steps and tested lithium hydroxide-containing mother liquor in a process for the preparation of lithium transition metal phosphates, for example according to the DE-10353266 or the WO 02/083555 can be used by mixing it with an acidic solution containing phosphoric acid and at least one transition metal sulfate.

The inventive method thus provides a Circular process ready, at the same time the production of pure phase Barium sulfate and lithium transition metal phosphates allows, so a closed sewage system or a Sewage cycle is obtained, which is both particularly environmentally friendly and also economically efficient.

The invention is based on some embodiments and the figures be wrote without them being understood as limiting.

It demonstrate

1a a SEM image of barium sulfate particles precipitated at 40 ° C,

1b the particle size distributions of the filter cake,

2a a SEM image of the precipitated at a temperature of 80 ° C barium sulfate

2 B a diagram of the particle size distribution of the product,

Comparative Example 1

Precipitation of BaSO ₄ at room temperature

A lithium sulfate-containing wastewater from a wet-chemical production process for lithium iron phosphate according to the DE 10353266 is adjusted to pH 10 by addition of lithium hydroxide, filtered on a paper filter, acidified to pH 5 with sulfuric acid and evaporated in the laboratory flask to a concentration of 148 g / l lithium sulfate. The X-ray diffraction spectrum of the filtered precipitate shows lithium phosphate. 105 ml of the concentrated lithium sulfate solution, are stirred in a 200 ml beaker on a magnetic stirrer with not activated heating plate. 26.78 g of finely powdered technical barium hydroxide monohydrate are added within 10 sec. The result is a white suspension whose viscosity initially rises rapidly and then falls slowly again. The suspension is further stirred for 20 minutes and filtered off on a paper filter. The filtrate is separated and the filter cake washed with demineralized water to a conductivity of less than 150 μS / cm. The particle size distribution of the still wet filter cake is measured in a Malvern Mastersizer in ethanol with ultrasonic fingers. The measured particle size distribution is trimodal with D10 = 0.4 μm, D50 = 3.0 μm, D90 = 33 μm. The filter cake is dried at 60 ° C overnight and ground on a laboratory Siebrotormühle (Fritsch Pulverisette 14). The X-ray diffraction spectrum of the dried and ground filter cake did not show phase-pure barium sulfate. The scanning electron micrograph showed stacked aggregated thin-plate particles.

Comparative Example 2

Precipitation of BaSO ₄ at 40 ° C

The procedure was as in Comparative Example 1, but the solution is heated to 40 ° before the addition of the barium hydroxide with the hot plate. In the 1b shown particle size distribution of the still wet filter cake is bimodal with D10 = 0.4 microns, D50 = 4.7 microns, D90 = 24 microns. The X-ray diffraction spectrum of the dried and ground filter cake did not show phase-pure barium sulfate. The scanning electron micrograph in 1a shows strongly agglomerated irregularly shaped fine particles.

example 1

Precipitation of BaSO ₄ at 80 ° C

The procedure was analogous to Comparative Example 1, but the solution was heated to 80 ° before the addition of the barium hydroxide with the hot plate. In the 2 B shown particle size distribution of the still wet filter cake is monomodal with D10 = 0.3 microns, D50 = 0.6 microns, D90 = 1.9 microns. The X-ray diffraction spectrum of the dried and ground filter cake had only a phase-pure barium sulfate. The scanning electron micrograph in 2a shows well-separated, relatively smooth roundish particles. The BET specific surface area of the product was 10 m ² / g. The whiteness according to R457 is 97.2 and the yellowness value is 1.02.

In the control study described above, test tube A shows a slight haze and test tube B no haze. The composition of the obtained lithium hydroxide solution determined by ICP analysis was:
Li ⁺ 18.1 g / l
SO ₄ ² 132 mg / l
PO ₄ ^3-10 mg / l
Fe ²⁺ 1 mg / l
Ba ²⁺ 0.2 mg / l

she is thus excellent as a raw material for a wet chemical Synthesis of lithium transition metal mixed phosphates suitable.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 01/92157 [0004]
• WO 01/58809 [0008]
• WO 00/76919 [0010]
• US 5910382 [0011]
• WO 02/099913 [0011]
• - DE 10353266 [0012, 0031, 0037, 0045]
• WO 02/083555 [0012, 0031, 0037]

Cited non-patent literature

• - J. Hocken in Euro Coat, Lyon 9/97 pages 1 to 14 [0004]
• Machunsky, E. Winkler, J., Polymers Paint Color Journal (1990) 180, 350-354 [0006]

Claims (16)

Circular process for the production of barium sulfate and Lithium transition metal phosphates comprising the (I) Providing an aqueous, lithium and sulfationhaltigen Solution and (ii) adding solid barium hydroxide at a temperature of more than 50 ° C, (iii) where the addition of the barium hydroxide over a period of less than 15 minutes. Method according to claim 1, characterized in that that the process is carried out in the absence of seed crystals becomes. Method according to claim 2, characterized in that that the addition of the solid barium hydroxide in less than 5 minutes he follows. Method according to claim 3, characterized during and after the addition of the solid barium hydroxide the mixture is stirred. Method according to claim 4, characterized in that that the resulting barium sulfate is separated from the mother liquor becomes. Method according to claim 5, characterized in that that the lithium hydroxide-containing mother liquor with an acidic solution, containing phosphoric acid and at least one transition metal sulfate is mixed. Method according to one of the preceding claims, characterized in that the aqueous lithium and sulfate ions containing solution from step i) before implementation of step ii) is pretreated by adding lithium hydroxide and is adjusted to a pH above 10 and wherein the resulting precipitate is separated. Method according to claim 7, characterized in that that the separated precipitate is used as starting material for Production of lithium metal phosphates is used. Method according to claim 8, characterized in that that the separated precipitate by acidification is converted to easily soluble lithium hydrogen phosphate. Method according to claim 7, characterized in that that the pretreated lithium sulfate containing solution a concentration by reverse osmosis is supplied. Method according to claim 10, characterized in that that the pretreated lithium sulfate containing solution neutralized before the reverse osmosis by adding sulfuric acid or slightly acidic to a pH between 7 and 2 is set. Barium sulfate obtainable by the method according to any one of claims 1 to 5, having an average particle diameter in the range of 0.5 to 1 μm. Barium sulfate according to claim 12, characterized in that that a monomodal particle distribution with a D50 value of 0.6 microns is present. Barium sulfate according to claim 13, characterized in that that it is free from chloride and / or sulphide. Barium sulfate according to claim 14, characterized in that that it is alkali-free. Barium sulfate according to any one of claims 12 to 15 with a whiteness of greater than 95th